Many women felt a boost of optimism from the historic nature of this appointment. TechCrunch postulated that she may be the first pregnant Fortune 500 CEO. And even if she weren’t expecting, there are few women at the helm of large tech companies, so adding another is still a pretty big deal. (The number of women running a Fortune 500 company jumped 5 percent yesterday, from nineteen to twenty.)

But will she help make progress like hers possible for other women? That’s an open question. Remember that Atlantic article by Ann-Marie Slaughter a few weeks ago about work-family balance? One of Slaughter’s key goals for creating a work environment that’s more family-friendly is to get women into positions of power. She wrote, “The best hope for improving the lot of all women…is to close the leadership gap: to elect a woman president and 50 woman senators; to ensure that women are equally represented in the ranks of corporate executives and judicial leaders.” It would seem, then, that just having Mayer in the job would necessarily lead to greater gender equality.

But the problem with Slaughter’s hypothesis is that this form of “trickle-down feminism,” as coined by Tressie McMillan Cottom, may not in fact trickle down. In her exclusive interview with Fortune announcing the pregnancy, Mayer was already talking tough about working through her maternity leave. “I like to stay in the rhythm of things,” she told Fortune. “My maternity leave will be a few weeks long and I’ll work throughout it.”

That may be easy for her to say, but her behavior will inevitably become the model for what’s considered the norm for all the women working under her. If the boss is only out a few weeks and doesn’t even take real time off of work, why should a lower-down pregnant employee expect that she could take the full twelve (unpaid) weeks allotted to her by the FMLA and not raise a few eyebrows?

The problem is not that Mayer doesn’t care about women’s equality. It’s that because she’s achieved so much, she seems to assume there are boundless opportunities for all women, which they just have to take advantage of like she did. This is crystal clear in a short interview she did with Makers about not being a feminist:

Here’s the transcript of what she says:

I don’t think that I would consider myself a feminist. I think that I certainly believe in equal rights, I believe that women are just as capable, if not more so in a lot of different dimensions, but I don’t, I think have, sort of, the militant drive and the sort of, the chip on the shoulder that sometimes comes with that. And I think it’s too bad, but I do think that feminism has become in many ways a more negative word. You know, there are amazing opportunities all over the world for women, and I think that there is more good that comes out of positive energy around that than comes out of negative energy.

I don’t really want to comment on her characterizations of feminism. It appears that Mayer has absorbed the caricature of feminists as downers on the warpath.

What I want to focus on is her intimation that feminism’s work has been accomplished. Yes, she is living proof of the growing opportunities that are opening to women. If she made it to the top, why can’t other women? As she says in another clip with Makers, “The situation for women in technology has changed.… There’s huge growth and huge opportunity.” That’s clearly true a few days after Yahoo! decided to put a pregnant woman in charge. Her own life story appears to be one in which there were few barriers to her advancement in technology: she says that she was “gender oblivious” in childhood, never being made aware that she was an anomaly in the computer science classrooms.

But women are still a measly 4 percent of Fortune 500 CEOs. Why haven’t more women gotten to the top job? It’s a question that has also faced another powerful woman in technology: Sheryl Sandberg. Sandberg became famous for a TED talk in which she told women that to get ahead, they need to “sit at the table” and not “leave before you leave” to have a child.

You can read between the lines in Sandberg’s talk to her message that the heart of the problem lies with women and their behavior. Or you can listen to some other advice Sandberg doled out at a meeting of female Facebook executives for the company’s Women’s Leadership Day. As Ken Auletta reported in the The New Yorker, she told the group that while “there are still institutional problems…too much of the conversation is on blaming others, and not enough is on taking responsibility ourselves.” Exchanging stories about encountering sexism, Auletta writes, would only have “divert[ed] women from self-improvement.”

This is what’s hanging in the background when Mayer says, “there are amazing opportunities all over the world for women, and I think that there is more good that comes out of positive energy around that than comes out of negative energy.” It’s a tricky situation: clearly there are increased opportunities for women and Mayer and Sandberg are the proof of that. But their own personal success seems to make them think that such opportunities are now readily available to all women. If this were true, though, we would see a much better gender balance at the top and improved work-family policies.

As I wrote in response to Slaughter’s piece, there are still plenty of structural barriers in women’s way as they try to advance. While a few Mayers and Sandbergs have made it through, Catalyst research shows the pipeline isn’t leaky, making women choose to drop out. It’s blocked—they just can’t make it up. The positive changes women have experienced—many of them hard-won—can be celebrated without crowding out thinking about the challenges that still very much remain.

Given that Mayer’s new position was only announced two days ago, we’ll have plenty of time to see how she handles such questions as advancing women and creating family-friendly work environments. And her own experiences with parenthood may help inform her view on whether it can be hard to find balance between work and the rest of your life. But it’s clear that just getting women into high ranks doesn’t mean that they will necessarily come in ready to change policies like maternity leave to make it easier for their employees or recognize the struggles women go through as they try to climb the ladder. Another woman CEO is historic, but it’s far from the change we need for women’s workplace equality.

Bryce CovertTwitterBryce Covert is a contributor at The Nation and a contributing op-ed writer at The New York Times.